Since the lackluster response to Birth of the Federation, we've suffered through a dearth of turn-based space strategy games. Certainly Homeworld addressed the needs of real-time gamers (and a lot of others, garnering one of our "Best of 1999" awards), but for those who prefer the pace and cerebrally of turn-based, there hasn't been much out there since Master of Orion (1 & 2).
From mainstream publishers, that is. Malfador Machinations has been working the side streets and alleys of the marketplace, turning heads and catching disproportionate attention for their Space Empire series for some years, including winning a number of "best of's" despite their almost complete lack of publicity, marketing, or coverage. Nonetheless, they have remained one of those 'inside secrets' of the genre - a great set of games that few knew about.
With Space Empires IV, they may have finally crested into the mass market. More of a evolutionary than revolutionary upgrade, SE4 leaves its predecessor SE3 far behind in many ways while still managing to cling to the core concepts that made SE3 such a great game.
First, SE4 has the basic formula down pat as somewhere between MOO and VGAP/Stars!. There are (essentially) 3 main resources - minerals, organics, and radio actives. Plunder planets for these, use them to build planetary facilities, bases, and ships to conquer or colonize the next set of planets. The stellar systems are connected by warp points which can vary from large, fixed and stable warp point to small (limiting the size of ship that can pass through), unstable (flickering), or even one-way gates that will really screw up your expansion plans. Other races are also out there in the great beyond somewhere, waiting to be your friend or eat your colonists, you never really know which.
Second, there's a serious esthetic and usability upgrade since SE3, evolving from the nice-but-merely-adequate graphics that were common for its other self-published brethren, to 24-bit rendered graphics and a tight, easily-understood menu/button structure that would be the proud product of any big studio.
To really understand the quality of SE4, first sit down and ask yourself, seriously: what do I want in a turn-based space strategy game? I have very little doubt that the near-entirety of your list will already be a part of SE4. Scope? From small games with 20 stellar systems (perfect for online play) to massive galactic sectors of 100 systems which make for a better long terms solo game, the player has complete control. Each system can have upwards of 15 planets, planetoids and asteroid fields to colonize/exploit in each system, suggesting that in the longest games, you could conceivably have to seize and hold at least 500 worlds before your opponents will start conceding the game. Flexibility? There are 10 races included in the game -each race has 15 traits, 13 cultural stereotypes (xenophobic, etc.), even a number of different portraits and ship architecture to choose from. Still not enough? Almost everything in the game is in easily accessible files in common formats, so if you want to add your OWN picture, it's just a *.bmp away. Add a new race, customize the traits in 1% increments (!), you can play essentially whatever you want. The game systems themselves are managed by rules laid out neatly in txt files, so you can also adjust the rules to your heart's content.
Moreover, the game is littered with random events, secret tech trees, and even (at the very highest tech levels) the ability to destroy or create planets, suns and even warp points, critically affecting the entire map geography.
There are a staggering variety of technologies (according to Malfador: hundreds of levels. 500+ components and 300+ planetary facilities), with which to equip your ships and planets. Ships are built like the old tabletop game Starfire - within a given weight for a hull size, components are added in linear order, left to right. Damage in combat is applied from right to left, giving would-be ship designers some strategic choice even at the ship-design level. Do you put your guns to the right of engines, allowing semi-damaged ships to (hopefully) escape to fight another day? Or do you put the engines to the right of the guns, protecting your weapons possibly the few more moments needed to win a critical fight?
The AI knows, that's for sure. Even on easy levels, the AI in SE3 was formidable and I expect it in SE4 to be equally so. (And this is with an AI that doesn't cheat - such is the statement of the designer AND the opinion of thousands of happy SE3 fans.) Nothing's quite so frightening as cheering when your Space Yards develop the ability to build cruiser-sized ships, only to gasp as that alien Dreadnought shows up on your doorstep. Not a good feeling, and one that few enough titles are able to credibly give even a beginner, much less an experienced player (as SE3 was prone to do all too often).
But that doesn't mean you're at its mercy - there are more than 20 "minister" AI's that you can freely put to work on your behalf, using the same algorithms the computer's using. Enabling these doesn't emasculate the player, either. Their fields of expertise can be very narrow, such as "refits", "scrapping", or "mining" - leaving the fun for the player. For example, I typically will assign the management of upgrades (the task of keeping your fleet at the cutting edge technologically) to a minister. The scope of tech development, and the speed in later turns makes the task of micromanaging this almost more than I can handle.
I really can't overstate the options available to you as a player in SE4. Like carrier battles? The tech tree for the development and management of primarily fighter-wielding fleets is there. Prefer to play an economic game? Full trading and economic systems are present, including purely defensive systems like Monitors and mines to keep those trading lanes open. Intelligence operations, intricate diplomatic options for dealing with other players (and an AI diplomatic behavior that is far superior even to what was in MOO2, for example) and even a combat simulator to test those new designs before putting them in the field - it's all there.
Additionally, SE4 comes with a handy suite of tools embedded throughout the interface for keeping tabs on what is happening, such as the diplomatic map where you can flag systems (for yourself) as "don't go there" - a handy tool for a large human-run empire and critical to make sure the Minister AI (if enabled) doesn't screw up something accidentally.
Solo gameplay aside, SE4 is really meant to be played online. The AI is nasty, but nothing beats the sheer cunning of a hominid brain at the other end of that internet connection. Multiplay - up to ten humans, not counting the AI's - is via PBEM, so the turns (which can start taking major amounts of time given the game's possible scope) can be played offline. To get a very good feel for what SE4 is going to be, SE3 is available in tech-crippled (but fully functional) demo (a puny 2.7meg D/L) - I highly recommend it.
Malfador has already included everything I could think of - I'm not kidding. Somehow they have a very good handle on everything that I, as a gamer, wanted - and will want - in this game. I can't wait until it comes out.